Police in South Korea vowed Sunday to find those responsible for the previous evening’s violence in central Seoul, as 74 officers were injured in clashes with demonstrators calling for justice following last year’s Sewol ferry disaster.

At least nine protesters also had to be hospitalized.

Thursday marked the first anniversary of the death of 304 people in the Sewol’s sinking off South Korea’s southwestern coast – many of whom were local high school students on a field trip.

Family members and their supporters have for months been campaigning for an independent investigation into the disaster, the authorities’ response to it, and related corruption allegations.

Among multiple court cases, the toughest punishment handed out so far has been for the ferry’s captain, who was sentenced to 36 years in prison after abandoning the Sewol when the majority of passengers were still obeying instructions to stay below deck.

Frustration with the government boiled over Saturday after thousands had gathered in front of Seoul City Hall – though they were matched by more than 13,000 police officers.

The clashes began when protesters attempted to make their way towards the presidential office.

More than 70 police vehicles were damaged or even tipped over – some sprayed with graffiti slogans calling for President Park Geun-hye’s resignation.

Park is currently in South America, after embarking on a four-nation tour on the same day as the Sewol disaster’s anniversary.

A Seoul Metropolitan Police Agency spokesperson told reporters Sunday that they would “run after those who organized the violent rally and acted violently so they could be subjected to legal punishment.”

One hundred demonstrators were taken into custody amid the chaos, including 20 family members of Sewol victims.

On Sunday, rain fell on a small group of protesters as they remained in Seoul’s iconic Gwanghwamun Square, situated between City Hall and the presidential office.

In front of them were images of the nine still missing Sewol passengers – their loved ones waiting for the realization of the president’s promise to salvage the sunken ferry as soon as possible.